lcd panel input lag quotation

One of the areas where the A-MVA panel does extremely well is in the areas of display lag and pixel response time. Just to recap, you may have heard complaints about "input lag" on various LCDs, so that"s one area we look at in our LCD reviews. We put input lag in quotation marks because while many people call it "input lag", the reality is that this lag occurs somewhere within the LCD panel circuitry, or perhaps even at the level of the liquid crystals. Where this lag occurs isn"t the concern; instead, we just want to measure the duration of the lag. That"s why we prefer to call it "processing lag" or "display lag".

To test for display lag, we run the Wings of Fury benchmark in 3DMark03, with the output set to the native LCD resolution - in this case 1920x1200. Our test system is a quad-core Q6600 running a Radeon HD 3870 on a Gigabyte GA-X38-DQ6 motherboard - we had to disable CrossFire support in order to output the content to both displays. We connect the test LCD and a reference LCD to two outputs from the Radeon 3870 and set the monitors to run in clone mode.

The reference Monitor is an HP LP3065, which we have found to be one of the best LCDs we currently possess in terms of not having display lag. (The lack of a built-in scaler probably has something to do with this.) While we know some of you would like us to compare performance to a CRT, that"s not something we have around our offices anymore. Instead, we are looking at relative performance, and it"s possible that the HP LP3065 has 20ms of lag compared to a good CRT - or maybe not. Either way, the relative lag is constant, so even if a CRT is faster at updating, we can at least see if an LCD is equal to or better than our reference display.

While the benchmark is looping, we snap a bunch of pictures of the two LCDs sitting side-by-side (using a relatively fast shutter speed). 3DMark03 shows the runtime with a resolution of 10ms at the bottom of the display, and we can use this to estimate whether a particular LCD has more or less processing lag than our reference LCD. We sort through the images and discard any where the times shown on the LCDs are not clearly legible, until we are left with 10 images for each test LCD. We record the difference in time relative to the HP LP3065 and average the 10 results to come up with an estimated processing lag value, with lower numbers being better. Negative numbers indicate a display is faster than the HP LP3065, while positive numbers mean the HP is faster and has less lag.

It"s important to note that this is merely an estimate - whatever the reference monitor happens to be, there are some inherent limitations. For one, LCDs only refresh their display 60 times per second, so we cannot specifically measure anything less than approximately 17ms with 100% accuracy. Second, the two LCDs can have mismatched vertical synchronizations, so it"s entirely possible to end up with a one frame difference on the time readout because of this. That"s why we average the results of 10 images, and we are confident that our test procedure can at least show when there is a consistent lag/internal processing delay. Here is a summary of our results for the displays we have tested so far.

As you can see, all of the S-PVA panels we have tested to date show a significant amount of input lag, ranging from 20ms up to 40ms. In contrast, the TN and S-IPS panels show little to no processing lag (relative to the HP LP3065). The BenQ FP241VW performs similarly to the TN and IPS panels, with an average display lag of 2ms - not something you would actually notice compared to other LCDs. Obviously, if you"re concerned with display lag at all, you"ll want to avoid S-PVA panels for the time being. That"s unfortunate, considering S-PVA panels perform very well in other areas.

Despite what the manufacturers might advertise as their average pixel response time, we found most of the LCDs are basically equal in this area - they all show roughly a one frame "lag", which equates to a response time of around 16ms. In our experience, processing lag is far more of a concern than pixel response times. Taking a closer look at just the FP241VW, we can see the typical one frame lag in terms of pixel response time. However, the panel does appear to be a little faster in response time than some of the other panels we"ve tested (notice how the "ghost image" isn"t as visible as on the HP LP3065), and we didn"t see parts of three frames in any of the test images.

After the initial article went live, one of our readers who works in the display industry sent me an email. He provides some interesting information about the causes of image lag. Below is an (edited) excerpt from his email. (He wished to remain anonymous.)

PVA and MVA have inherent drawbacks with respect to LCD response time, especially gray-to-gray. To address this shortcoming, companies have invested in ASICs that perform a trick generically referred to as "overshoot." The liquid crystal (LC) material in *VA responds sluggishly to small voltage changes (a change from one gray level to another). To fix this, the ASIC does some image processing and basically applies an overvoltage to the electrodes of the affected pixel to spur the LC material into rapid movement. Eventually the correct settling voltage is applied to hold the pixel at the required level matching the input drive level.

It"s very complicated math taking place in the ASIC in real time. It works well but with an important caveat: it requires a frame buffer. What this means is that as video comes into the panel, there is a memory device that can capture one whole video frame and hold it. After comparing it to the next incoming frame, the required overshoot calculations are made. Only then is the first captured frame released to the panel"s timing controller, which is when the frame is rendered to the screen. As you may have already guessed, that causes at least one frame time worth of lag (17ms).

Some companies discovered some unintended artifacts in their overshoot calculations and the only way they saw to correct these was to allow for their algorithm to look ahead by two frames instead of one. So they had to up the memory of the frame buffer and now they started capturing and holding not one but two frames upon which they make their complex overshoot predictions to apply the corrected pixel drive levels and reduce gray-to-gray response time (at the expense of lag time). Again, it works very well for improving response time, but at the expense of causing lag, which gamers hate. That in a nutshell is the basis of around 33ms of the lag measured with S-PVA.

Not every display uses this approach, but this could account for the increase in display lag between earlier S-PVA and later S-PVA panels. It"s also important to note that I tested the Dell 2408WFP revision A00, and apparently revision A01 does not have as much lag. I have not been able to confirm this personally, however. The above also suggest that displays designed to provide a higher image quality through various signal processing techniques could end up with more display lag caused by the microchip and microcode, which makes sense. Now all we need are better algorithms and technologies in order to reduce the need for all of this extra image processing -- or as we have seen with some displays (particularly HDTVs), the ability to disable the image processing.

Display lag is a phenomenon associated with most types of liquid crystal displays (LCDs) like smartphones and computers and nearly all types of high-definition televisions (HDTVs). It refers to latency, or lag between when the signal is sent to the display and when the display starts to show that signal. This lag time has been measured as high as 68 ms,Hz display. Display lag is not to be confused with pixel response time, which is the amount of time it takes for a pixel to change from one brightness value to another. Currently the majority of manufacturers quote the pixel response time, but neglect to report display lag.

For older analog cathode ray tube (CRT) technology, display lag is nearly zero, due to the nature of the technology, which does not have the ability to store image data before display. The picture signal is minimally processed internally, simply for demodulation from a radio-frequency (RF) carrier wave (for televisions), and then splitting into separate signals for the red, green, and blue electron guns, and for the timing of the vertical and horizontal sync. Image adjustments typically involve reshaping the signal waveform but without storage, so the image is written to the screen as fast as it is received, with only nanoseconds of delay for the signal to traverse the wiring inside the device from input to the screen.

For modern digital signals, significant computer processing power and memory storage is needed to prepare an input signal for display. For either over-the-air or cable TV, the same analog demodulation techniques are used, but after that, then the signal is converted to digital data, which must be decompressed using the MPEG codec, and rendered into an image bitmap stored in a frame buffer.

While the pixel response time of the display is usually listed in the monitor"s specifications, no manufacturers advertise the display lag of their displays, likely because the trend has been to increase display lag as manufacturers find more ways to process input at the display level before it is shown. Possible culprits are the processing overhead of HDCP, Digital Rights Management (DRM), and also DSP techniques employed to reduce the effects of ghosting – and the cause may vary depending on the model of display. Investigations have been performed by several technology-related websites, some of which are listed at the bottom of this article.

LCD, plasma, and DLP displays, unlike CRTs, have a native resolution. That is, they have a fixed grid of pixels on the screen that show the image sharpest when running at the native resolution (so nothing has to be scaled full-size which blurs the image). In order to display non-native resolutions, such displays must use video scalers, which are built into most modern monitors. As an example, a display that has a native resolution of 1600x1200 being provided a signal of 640x480 must scale width and height by 2.5x to display the image provided by the computer on the native pixels. In order to do this, while producing as few artifacts as possible, advanced signal processing is required, which can be a source of introduced latency. Interlaced video signals such as 480i and 1080i require a deinterlacing step that adds lag. Anecdotallyprogressive scanning mode. External devices have also been shown to reduce overall latency by providing faster image-space resizing algorithms than those present in the LCD screen.

Many LCDs also use a technology called "overdrive" which buffers several frames ahead and processes the image to reduce blurring and streaks left by ghosting. The effect is that everything is displayed on the screen several frames after it was transmitted by the video source.

Display lag can be measured using a test device such as the Video Signal Input Lag Tester. Despite its name, the device cannot independently measure input lag. It can only measure input lag and response time together.

Lacking a measurement device, measurement can be performed using a test display (the display being measured), a control display (usually a CRT) that would ideally have negligible display lag, a computer capable of mirroring an output to the two displays, stopwatch software, and a high-speed camera pointed at the two displays running the stopwatch program. The lag time is measured by taking a photograph of the displays running the stopwatch software, then subtracting the two times on the displays in the photograph. This method only measures the difference in display lag between two displays and cannot determine the absolute display lag of a single display. CRTs are preferable to use as a control display because their display lag is typically negligible. However, video mirroring does not guarantee that the same image will be sent to each display at the same point in time.

In the past it was seen as common knowledge that the results of this test were exact as they seemed to be easily reproducible, even when the displays were plugged into different ports and different cards, which suggested that the effect is attributable to the display and not the computer system. An in depth analysis that has been released on the German website Prad.de revealed that these assumptions have been wrong. Averaging measurements as described above lead to comparable results because they include the same amount of systematic errors. As seen on different monitor reviews the so determined values for the display lag for the very same monitor model differ by margins up to 16 ms or even more.

Several approaches to measure display lag have been restarted in slightly changed ways but still reintroduced old problems, that have already been solved by the former mentioned SMTT. One such method involves connecting a laptop to an HDTV through a composite connection and run a timecode that shows on the laptop"s screen and the HDTV simultaneously and recording both screens with a separate video recorder. When the video of both screens is paused, the difference in time shown on both displays have been interpreted as an estimation for the display lag.16 ms or even more.

Display lag contributes to the overall latency in the interface chain of the user"s inputs (mouse, keyboard, etc.) to the graphics card to the monitor. Depending on the monitor, display lag times between 10-68 ms have been measured. However, the effects of the delay on the user depend on each user"s own sensitivity to it.

Display lag is most noticeable in games (especially older video-game consoles), with different games affecting the perception of delay. For instance, in PvE, a slight input delay is not as critical compared to PvP, or to other games favoring quick reflexes like

If the game"s controller produces additional feedback (rumble, the Wii Remote"s speaker, etc.), then the display lag will cause this feedback to not accurately match up with the visuals on-screen, possibly causing extra disorientation (e.g. feeling the controller rumble a split second before a crash into a wall).

TV viewers can be affected as well. If a home theater receiver with external speakers is used, then the display lag causes the audio to be heard earlier than the picture is seen. "Early" audio is more jarring than "late" audio. Many home-theater receivers have a manual audio-delay adjustment which can be set to compensate for display latency.

Many televisions, scalers and other consumer-display devices now offer what is often called a "game mode" in which the extensive preprocessing responsible for additional lag is specifically sacrificed to decrease, but not eliminate, latency. While typically intended for videogame consoles, this feature is also useful for other interactive applications. Similar options have long been available on home audio hardware and modems for the same reason. Connection through VGA cable or component should eliminate perceivable input lag on many TVs even if they already have a game mode. Advanced post-processing is non existent on analog connection and the signal traverses without delay.

A television may have a picture mode that reduces display lag for computers. Some Samsung and LG televisions automatically reduce lag for a specific input port if the user renames the port to "PC".

LCD screens with a high response-time value often do not give satisfactory experience when viewing fast-moving images (they often leave streaks or blur; called ghosting). But an LCD screen with both high response time and significant display lag is unsuitable for playing fast-paced computer games or performing fast high-accuracy operations on the screen, due to the mouse cursor lagging behind.

Most computer engineers would define a display’s input lag as being the difference in time between the output from a graphics card, to the time that image is displayed on the screen. There are other factors which constitute “lag” which we will discuss on this page, and which ones you should be the most concerned about when looking to purchase a display or device for gaming.

It is worth noting that the display tests measure a different type of lag than the peripheral devices tests, and that the phrase “Input Lag” has no actual defined measurement by computer scientists. Display input lag is concerned with the time required for the pixels to show an image after it has been processed and sent by the graphics card. This is different than the manufacturers quoted pixel responsiveness time (such as GTG response time, or BTW – more on this in a bit), which measures how quickly the pixels can change from one color to another. Pixel response times are what affect things like motion blurring and ghosting – which also an important measure for gamers needing maximum performance for fast paced games.

The amount of lag varies greatly depending on the display, hence why there is a noted difference between manufacturers gaming displays vs their normal ones for casual/business use. It’s become commonplace for manufacturers to focus on gaming displays to provide the fastest response times and lowest input lag possible for the type of panel being used. The difference in lag depends on the internals of a monitor, such as its internal circuit board and scaling chips, which determine its signal processing time and therefore its quoted input lag and responsiveness. Many manufacturers take active measures for their gaming displays to reduce input lag as much as possible, with many offering modes which can bypass the scaling chips and including other options to reduce the input lag.

Short answer:input lag is caused by a combination of two things – the signal processing delay caused by the monitor’s internal electronic board, and the response time of the pixels.

“Input Lag” is made up of 2 parts. When a signal is sent from the GPU to a screen, the instant it hits the port on the back of the monitor/TV it begins what we would define as “Input Lag”. As the signal enters the display, it has 2 sections of lag, which can be measured.

Pixel Responsiveness Lag (The lag from the time is takes for the pixels to change to show the image after it was processed by the monitor’s internal circuit board).

Because the quoted pixel responsiveness time provided by the manufacturer is usually found to be pretty accurate (after comparing our tests to their quoted times), on InputLag.com we only focus on reporting this number.

Poor) A lag of more than 66.6ms / more than 2 frames at 30Hz – Very noticeable/distracting lag. Early LCD’s from the 1990’s may be this bad, but they do not exist now.

If the monitor has one frame of lag, it won’t really be noticeable because there are 144 frames being shown every second. However, a monitor running at only 30 FPS, skipping one frame constantly from the input lag is going to be much more noticeable, and put you at a significant disadvantage.

There are a few main reasons for this, most notably is the lack of testing ability for higher framerates. Leo’s tool is limited to 1080p and 60Hz, while many of the top gaming monitors are way ahead of this, pushing 240Hz nowadays. It would not be accurate to be testing an expensive top-shelf gaming monitor with a native 240Hz refresh rate, with a tool that can only measure up to 60Hz. It forces you to measure the input lag of that 240Hz monitor at only 60Hz, which means the fastest it can possibly score is 16.67ms. Wait, what – the maximum visible display lag for 60Hz is 16.67ms? Yes.

For instance, if a 240Hz monitor is rated as “Excellent @240Hz”, it will still be rated “Excellent” at 60Hz. The refresh rate of a monitor has a direct impact on its input lag. A 60Hz monitor, for example, will never have a visible input lag below 16.67ms, because at 60Hz, the screen gets refreshed every 16.67ms (refresh to the bottom of the screen, see the next question for an explanation). So, if the overall input lag time is really 15ms, it doesn’t matter, because the lag time is less than the time for the screen to refresh the image, and it can’t be visibly measured. A 120Hz display halves that time to 8.3ms, and a 240Hz display further reduces it to 4.17ms.

This is a huge distinction that needs to be made. The web is full of misinformation concerning quoted “Input Lag” times, which often are only measuring the time it takes for the pixels to change from black to white, and is more of an indication of pixel response time rather than the true “input lag” that gamers are wanting to know for an advantage.

This is important to understand to get a good grasp of how monitors work and why there is always a difference in reported lag times. It also explains how some sites can quote an Input Lag time that is faster than the possible refresh time of the screen. LCD monitors refresh from top to bottom as seen below in the video.

Most people using Leo’s tool test the monitor and report the number from the middle of the screen, something that SMTT does as well. This is why the maximum visible display lag for 60Hz is 16.67ms, yet often gets reported as being lower for gaming displays running at 60Hz. If you test a 60Hz display with an exact quoted input lag time of 16.67ms (time to refresh to the last pixels at the bottom of the LCD panel), it should take roughly (just an estimate) 16.67ms/2 = 8.335ms to provide a reading in the middle of the display.

Output from Mouse/Keyboard/Controller -> Signal processed by Computer and Game -> Signal sent out to screen through HDMI/other cable (about 1/100th the speed of light [scienceline.ucsb.edu/getkey.php?key=2910]) -> monitor processes signal and sends to panel for display -> pixels on panel change to show image as intended.

What is highlighted in red is what we are measuring for the “Input Lag” of a display (TVs & Monitors). By using a tool to measure the screen going from white to black, it can only visibly measure

What is highlighted in blue is what I consider to be Physical Input Lag – the time it takes for your mouse/keyboard/controller to send the signal to your computer. There is significant room for variation here, hence why this category is also so important to gaming.

This is absolutely false. It’s true the human eye does have its own lag, and then there is the lag associated with reacting to what the eye sees (such as moving your thumb on a controller), but all of this takes place after the input lag described so far on this page. Factoring in this “human eye lag”, it would look something like this:

As you can see, the Input Lag of a display does matter. Any improvement in lag, whether it’s from the controller, the signal processing, the refresh rate, the computer itself, or even wearing the proper glasses – puts you at an advantage over someone who is on inferior equipment.

That being said, there is something to say about the lag times from human to human. Some of us are better at recognizing what is being displayed on a screen. Some of us are better at reacting to the change on a screen. This is why the pro player will win against a casual player 10 times out of 10 for a fast paced game – they have been practicing this talent, and may even have some sort of natural-born advantage (debatable). Either way, will shaving 10ms of lag off your game make you win every time? Probably not. But will shaving 10ms of lag off your game help you win more? Definitely.

This is the question with the most technical jargon to comprehend. Data in a cable (in the form of an electrical frequency) travels at about 1/100th the speed of light (source). So for any digital cable, we are talking about nanoseconds in lag, billionths of seconds. The lag is so small, and so insignificant, it makes no difference whatsoever to a professional gamer. When talking about other components of Input Lag, we are able to measure them in thousandths of seconds, so shaving off 10ms is a whole tenth of a second (it makes a difference). But cable speed is the most insignificant part of input lag by a large margin. What’s important to take away is that the monitor you purchase will always include a cable to support the highest refresh rate and resolution possible for that display. So this section shouldn’t matter too much, but for those interested here is the information anyway.

When it comes to monitors, there are a few vital metrics us gamers care about. One is response time, how quickly a panel can change colours or brightness, and the other is input lag. Manufacturers quote response time figures – although they are often misleading – but don’t quote input lag so as a reviewer it’s really important that I test it and report on it in my reviews so you, the prospective buyer, know what you are getting.

Let’s take a quick step back though – what is input lag? Well, in a perfect world, the instant you click your left mouse button to fire a shot at an enemy in game, it would instantly display that shot on your screen. Ok maybe accounting for the speed of electricity, which is roughly 90% the speed of light, and making a rough approximation of 5m of total wiring between your mouse, PC and monitor, it would display is about 0.18 nanoseconds. Pretty fast then.

Unfortunately, since your mouse runs on USB, best case right now you are using one of the 8000Hz options from people like Razer or Corsair and it takes just 125µs for the USB controller to receive your input. Then your PC needs to process that input, then the graphics card needs to draw a new frame which even in a game like CSGO with an RTX 3080 at 380FPS takes 2.6ms. Then, assuming you are not using a 360Hz monitor, the GPU likely has to wait until the monitor is ready to refresh which at 144Hz can take 6.9ms – by that time the GPU will have drawn at least 2 more frames that are ever so slightly newer. Then, and only then, can the monitor process the image, converting the digital frame into voltages for each one of the pixels, and subpixels, then applying those voltages to make what is being displayed change.

It’s a lot, I know. Now what I just described is total system latency, and is one of the two ways to measure a monitor’s input lag. The other is to cut out the PC and measure just the monitor on it’s own. While less of a ‘real world’ measurement, it provides an easy and direct comparison between monitors and takes any performance issues with the system out of the equation. Personally, I like to quote both figures in my reviews so you can get the best understanding possible before making a purchasing decision.

When it comes to total system input lag, there are a few different ways you can measure it. Potentially the most obvious way is with a camera. Now just recording at 30 or 60 FPS won’t give you very good results, as each recorded frame will be 33ms or 16.7ms apart, so for measuring something that can be just a couple of milliseconds, that’s not very helpful. Recording at 240FPS is better, as each frame is captured every 4.2ms, but that’s still not a good resolution to measure this with, so the normal go-to is 1000FPS. That means a frame captured every 1ms, and it’s what I use with my Sony RX100 Mark 5A, technically 960FPS but I factor that into my measurements. But it’s no good just spamming a mouse button and recording it, because you won’t know when the mouse actually registers the click and sends it to the PC – hence why I soldered an LED directly to the switch.

As ApertureGrille showed in his video on input lag – one you should definitely go watch by the way I’ll leave that in the cards above – you can use an LDR or light dependant resistor (my A Level Electronics is finally paying off…) to measure brightness changes on screen using an arduino. He made a UE4 project that changes the entire display colour from black to white with a keypress, and has the arduino do that a load of times and record the results. That’s great, but very much home-made, and while it’s more accurate for testing the monitor, it’s not the same ‘real world’ measurement that testing in a production game would give. It’s not what you the end user who bought one would experience.

Thanks for coming with me on the journey of explaining input lag, testing it and NVIDIAs sweet new tool, and I hope it’s been interesting and maybe you learned something. If you want to see more videos like this, or monitor reviews for that matter, hit that subscribe button and the bell notification icon.

While both input lag and response time are equally important for a fluid gaming experience, too high input lag can make competitive gaming unbearable.

So, a 120Hz display will have essentially half the input lag in comparison to a 60Hz display since the picture gets updated more frequently and you can react to it sooner.

Pretty much all new high refresh rate gaming monitors have low enough input lag in relation to their refresh rate that the delay between your actions and the result on the screen will be imperceptible.

For PC monitors and smart TVs, speed largely comes down to pixel response and input lag. They’re both measured in milliseconds, and they’re at least a little interrelated – but they’re not the same thing at all.

As for input lag, that’s a measure of the delay between signal output from a source device, such as a games console, set top box or PC, and the video image being shown on the display. And it’s all about feel. Does the screen respond quickly to your control inputs in a game? If it does, it has low lag or latency. If there’s a noticeable delay between wiggling a mouse or control pad and on-screen movement, then it probably suffers from significant lag.

Anyway, response and lag don’t apply in quite the same way to all display and panel types, be that OLED vs LCD or TVs and PC monitors (note that TVs and other screens marketed as ‘LED’ are typically LCD panels with LED backlights, not actually LED panels).

Shown on a graph, the pixel response of an LCD panel follows an ‘S’ curve, with a slightly sluggish immediate response, followed by that rapid middle phase, before response tails off dramatically towards the end of the transition. The net result is the time taken to fully transition from one color to another can be dramatically longer than the quoted GtG response.

In theory, MPRT response is a direct function of refresh rate. So, a refresh rate of 1000Hz is required to achieve a 1ms MPRT pixel response. However, mitigating measures including black-frame insertion or strobing backlights can improve MPRT response to below the refresh rate of the panel and to the point where it’s typically faster than a screen’s GtG response, at least in terms of quoted specifications.

The fastest current LCD panels are quoted at 1ms for GtG response and 0.5ms for MPRT response. But independent testing shows a whole different ballgame. Sources including Rtings.com and Linus Tech Tips peg full-transition pixel response from speedy OLED sets like LG C1 and CX panels at around two to three milliseconds, with the bulk of the transition (and thus the GtG equivalent performance) completed in a fraction of a millisecond.

Results for LCD technology vary a little more, probably due to methodology. But the best case scenario for an ultra-fast-IPS LCD monitor, such as the Asus ROG Swift 360Hz PG259QN, by comparison, is around 3ms for the bulk of the transition and 6ms for the full color change while other results push those two metrics out to 6ms and 10ms or more respectively. Either way, OLED is clearly faster.

The refresh rate of a screen puts a hard limit on the minimum latency or input lag it can achieve. To put some numbers on that, most mainstream monitors and TVs refresh at 60Hz or once every 16.67ms. Increase the refresh rate to 120Hz and the screen updates every 8.33ms.

Now, 16.67ms might not sound like a long time to wait – but should the screen require any time at all to process the signal, that latency will only increase, as those 16.67ms are also just the latency generated by your display. A PC or games console needs time to process a control input, feed it through the game engine and kick out frames in response. It all adds up.

Happily, some TVs now offer a dedicated low-latency game mode with minimal processing. Such TVs tend to be comparable to monitors running at the same refresh rate in terms of lag. The LG C1 OLED TV has been measured as low as 5ms at 120Hz. Intriguingly, running outside of game mode, the C1 is tragically slow at nearly 90ms, which neatly demonstrates just how much impact image processing can have.

In terms of refresh rate, the fastest current PC monitors can hit 360Hz, while the highest refresh TV sets accept an input signal of 120Hz. Some TVs have higher internal refresh rates of 240Hz or more, but in terms of latency or input lag, it’s the signal refresh from the source device that matters.

Long story short, the fastest OLED TVs deliver as little as 5ms of lag, while the quickest PC monitors including the aforementioned Asus panel along with other 360Hz monitors such as the Alienware AW2521H have been clocked at well under 2ms. So while OLED wins out on pixel response, certain LCD monitors have an advantage with input lag.

Apart from the differences discussed between GtG response and MPRT, IPS and VA panel types tend not to be entirely comparable. By that we mean that the subjective experience of a 1ms IPS panel is usually that little bit crisper, clearer and cleaner in terms of response than a VA panel. IPS, in short, tends to be faster.

What’s more, pretty much all gaming monitors offer user-configurable overdrive which can accelerate response but also introduce unwanted image quality issues such as overshoot and inverse ghosting. All those caveats aside, the latest 1ms IPS panels deliver the best performance with very low levels of blur, while 1ms VA monitors are just a little behind. The next rung down and probably the slowest you should consider for gaming is 4ms. Depending on the monitor in question, the panel type and the settings used, such screens may not differ that greatly in terms of the subjective experience. But the worst of them will have noticeably more blur than a 1ms display.

Beyond that, you’re into 7ms and beyond territory. On paper, that ought to be fine. But as we’ve seen, even the fastest LCD panels rated at 1ms can be measured at 10 times that long for real-world response. So quoted specifications should be viewed more as a tool with which to categorize screens than set expectations for actual performance.

But what of lag or latency? Most gamers will find a PC monitor with 144Hz refresh offers no noticeable lag and feels seriously slick and super quick. For really competitive esports competition there are small gains to be had from 240Hz and 360Hz displays. But for us? We’d be very happy with either a 120Hz OLED TV or a 144Hz 1ms monitor.Just want a good low-lag screen? Check out the best gaming monitors and best 120Hz TVsToday"s best gaming monitors and 120Hz TVs

For PC monitors and smart TVs, speed largely comes down to pixel response and input lag. They’re both measured in milliseconds, and they’re at least a little interrelated – but they’re not the same thing at all.

As for input lag, that’s a measure of the delay between signal output from a source device, such as a games console, set top box or PC, and the video image being shown on the display. And it’s all about feel. Does the screen respond quickly to your control inputs in a game? If it does, it has low lag or latency. If there’s a noticeable delay between wiggling a mouse or control pad and on-screen movement, then it probably suffers from significant lag.

Anyway, response and lag don’t apply in quite the same way to all display and panel types, be that OLED vs LCD or TVs and PC monitors (note that TVs and other screens marketed as ‘LED’ are typically LCD panels with LED backlights, not actually LED panels).

Shown on a graph, the pixel response of an LCD panel follows an ‘S’ curve, with a slightly sluggish immediate response, followed by that rapid middle phase, before response tails off dramatically towards the end of the transition. The net result is the time taken to fully transition from one color to another can be dramatically longer than the quoted GtG response.

In theory, MPRT response is a direct function of refresh rate. So, a refresh rate of 1000Hz is required to achieve a 1ms MPRT pixel response. However, mitigating measures including black-frame insertion or strobing backlights can improve MPRT response to below the refresh rate of the panel and to the point where it’s typically faster than a screen’s GtG response, at least in terms of quoted specifications.

The fastest current LCD panels are quoted at 1ms for GtG response and 0.5ms for MPRT response. But independent testing shows a whole different ballgame. Sources including Rtings.com and Linus Tech Tips peg full-transition pixel response from speedy OLED sets like LG C1 and CX panels at around two to three milliseconds, with the bulk of the transition (and thus the GtG equivalent performance) completed in a fraction of a millisecond.

Results for LCD technology vary a little more, probably due to methodology. But the best case scenario for an ultra-fast-IPS LCD monitor, such as the Asus ROG Swift 360Hz PG259QN, by comparison, is around 3ms for the bulk of the transition and 6ms for the full color change while other results push those two metrics out to 6ms and 10ms or more respectively. Either way, OLED is clearly faster.

The refresh rate of a screen puts a hard limit on the minimum latency or input lag it can achieve. To put some numbers on that, most mainstream monitors and TVs refresh at 60Hz or once every 16.67ms. Increase the refresh rate to 120Hz and the screen updates every 8.33ms.

Now, 16.67ms might not sound like a long time to wait – but should the screen require any time at all to process the signal, that latency will only increase, as those 16.67ms are also just the latency generated by your display. A PC or games console needs time to process a control input, feed it through the game engine and kick out frames in response. It all adds up.

Happily, some TVs now offer a dedicated low-latency game mode with minimal processing. Such TVs tend to be comparable to monitors running at the same refresh rate in terms of lag. The LG C1 OLED TV has been measured as low as 5ms at 120Hz. Intriguingly, running outside of game mode, the C1 is tragically slow at nearly 90ms, which neatly demonstrates just how much impact image processing can have.

In terms of refresh rate, the fastest current PC monitors can hit 360Hz, while the highest refresh TV sets accept an input signal of 120Hz. Some TVs have higher internal refresh rates of 240Hz or more, but in terms of latency or input lag, it’s the signal refresh from the source device that matters.

Long story short, the fastest OLED TVs deliver as little as 5ms of lag, while the quickest PC monitors including the aforementioned Asus panel along with other 360Hz monitors such as the Alienware AW2521H have been clocked at well under 2ms. So while OLED wins out on pixel response, certain LCD monitors have an advantage with input lag.

Apart from the differences discussed between GtG response and MPRT, IPS and VA panel types tend not to be entirely comparable. By that we mean that the subjective experience of a 1ms IPS panel is usually that little bit crisper, clearer and cleaner in terms of response than a VA panel. IPS, in short, tends to be faster.

What’s more, pretty much all gaming monitors offer user-configurable overdrive which can accelerate response but also introduce unwanted image quality issues such as overshoot and inverse ghosting. All those caveats aside, the latest 1ms IPS panels deliver the best performance with very low levels of blur, while 1ms VA monitors are just a little behind. The next rung down and probably the slowest you should consider for gaming is 4ms. Depending on the monitor in question, the panel type and the settings used, such screens may not differ that greatly in terms of the subjective experience. But the worst of them will have noticeably more blur than a 1ms display.

Beyond that, you’re into 7ms and beyond territory. On paper, that ought to be fine. But as we’ve seen, even the fastest LCD panels rated at 1ms can be measured at 10 times that long for real-world response. So quoted specifications should be viewed more as a tool with which to categorize screens than set expectations for actual performance.

But what of lag or latency? Most gamers will find a PC monitor with 144Hz refresh offers no noticeable lag and feels seriously slick and super quick. For really competitive esports competition there are small gains to be had from 240Hz and 360Hz displays. But for us? We’d be very happy with either a 120Hz OLED TV or a 144Hz 1ms monitor.Just want a good low-lag screen? Check out the best gaming monitors and best 120Hz TVsToday"s best gaming monitors and 120Hz TVs

To allow quick comparison between many display I"ve summarized the results across all the displays I"ve personally tested with the piLagTester Pro. Min lagis the first response at the top of the screen, real lag is the full response at the bottom. The list is sorted by 720p real lag, since all displays support that particular resolution.

You can see this display is quite competitive, with best of class input lag. Response time is a bit slow, but the sum is still very competitive. Despite the age it"s still one the fastest displays I"ve tested. It seems that TN displays have had low lag for a long time. On the other hand, the long response time means that motion will be kind of blurry, so I don"t think it"s a great choice for gaming.

I strongly prefer IPS panels for their accurate color over wide viewing angles. A good IPS display will cost more than a TN display, but will almost certainly be slower. If you are primarily concerned with gaming TN might be the way to go, though of course not every TN display is optimized for low lag and fast response.

I tested the Dell 1907FP model, which is the 19" version. There appears to be two versions of this panel: the 1907FP and the 1707FP . Based similarities in their names, specs and release date I suspect that they would perform similarly, just differing in pixels size.

Complicating things significantly, this is yet another display that does not actually sync to the input signal - instead it fills its own internal frame buffer from the video input and then draws that with a fixed additional delay that is randomly determined each time you turn on the set or switch inputs. The maximum draw rate is 59.94hz, so 60hz (or the "supported" 75hz) just drops frames in order to keep up. At least there"s no drift in the input lag for 59.94hz signals. Of zero relevance to gamers but still notable, it can draw the display at 50hz when given a 50hz signal (no doubled frames). So it might be good for watching movies.

Because of the lack of proper sync each time you turn on a new input you"ll get a different amount of input lag. To take one example, input lag for 720p will vary from 20ms to 36ms. What you get seems to be entirely up to chance. I"ve elected to report the average lag values here, since that seems fairest, but there"s no right answer; for more discussion of this issue see the above link.

I report two kinds of values. 1st response measures how long it takes for the TV to start responding (I use a 5% change in display brightness). This overly optimistic value doesn"t tell how long it takes to see anything useful, but matches what other reviewers call input lag. full response is a more realistic measure of lag, and requires the display to reach 80% of full brightness. This combines both input lag and response time, and is closer to what you would actually experience in a game.

Although you can spot cheaters in fps, because games do have native input lag from buffering codes. If the player always fires people at under 265ms, although the game native codes pull at least 96ms of lag, it mean the player react consistently at 169ms... Although human reaction time is usually around 250ms...